1. Field of the Invention
The present invention relates to a data storage device of the type that accepts a removable disk cartridge, and more particularly, to a mechanism to secure read/write heads at a predetermined safe position when the heads are supposed to be in the predetermined safe position.
2. Description of the Prior Art
Removable disk cartridges for storing digital electronic information typically comprise an outer casing or shell that houses a rotatable recording medium, or disk, upon which electronic information can be stored. The cartridge shell often comprises upper and lower halves that are joined together to house the disk. The disk is mounted on a hub that rotates freely within the cartridge. When the cartridge is inserted into a data storage device, e.g., disk drive, a spindle motor in the drive engages with the disk hub in order to rotate the disk within the cartridge. The outer shell of the cartridge typically has some form of opening near its forward edge to provide the recording heads of the drive with access to the recording surfaces of the disk. A shutter or door mechanism is often provided to cover the opening when the cartridge is not in use to prevent dust or other contaminants from entering the cartridge and settling on the recording surface of the disk.
Disk drives for receiving removable disk cartridges, including conventional 3.5" floppy disk drives, must have some mechanism for detecting the insertion or presence of a disk cartridge in the drive. The actuator that carries the recording heads of the disk drive across the recording surfaces of the disk should not be allowed to move unless the presence of a disk cartridge is detected. In the prior art, mechanical or electrical switches are typically employed to detect the presence of a disk cartridge within the drive. Such switches are typically positioned so that when a disk cartridge is inserted fully into the drive, the cartridge contacts the switch, thereby providing an indication that the disk cartridge is present.
After the cartridge is removed from the disk drive, the disk drive generally retrieves the read/write heads into a predetermined safe position so as to prevent any damage to the read/write heads. Such head retrieval usually relies on a signal from the above described switches. However, under certain circumstances, the absence of a disk cartridge in the disk drive may not be correctly detected by these switches. For example, power failure may disable an electrical switch. The failure of the disk detecting means in the absence of a disk cartridge in the disk drive may leave the heads at a unretracted position. Such unretracted heads are not protected from damage.
The above described head damage may also occur under different circumstances. A user may inappropriately eject or intentionally remove the cartridge from the drive when the heads are not yet retracted to a safe position. Regardless of the reason for the unretracted heads in the absence of the disk cartridge in the disk drive, the current invention is directed to solve the above described problem of damage to the unretracted read/write heads in a data storage device.